1. Field of the Invention
The present relates to a photographing object image adjusting apparatus and a photographing apparatus, and in particular to a photographing object image adjusting apparatus that performs focus and brightness adjusting for each photographing mode and a photographing apparatus having focus and brightness adjusting functions for each photographing mode.
2. Discussion of the Background
In photographing apparatuses, such as digital cameras, auto-focusing automatically adjusting the focus is performed so that an optimal image of a photographing object is imaged on an imaging surface. An auto-focusing method called a CCDAF (CCD auto-focusing) method is generally used in digital cameras. In the CCDAF method, while moving a focusing lens from the infinite distance side to the closest distance side to change the state of the focus, an image of a photographing object is imaged on an imaging surface of a CCD as a photographing element, high frequency components of image signals obtained from the CCD are sampled and evaluated, and the point where a maximum evaluation value has been obtained is determined as the focused position. A range in which a focusing lens or a CCD as a photographing element is moved for focus adjustment or auto-focusing is sometimes referred to as a scanning range for focus adjustment or auto-focusing, and the width of the range is referred to as the scanning width for focus adjustment or auto-focusing.
Driving a focus adjusting mechanism for moving a lens system or a CCD as photographing element must be controlled such that the lens system or the CCD is stopped with a resolution finer than a depth of focus, which is determined by an F-number and a focal distance of the lens system and a picture element pitch of the CCD. Otherwise, it occurs that, for example, when the lens system is out of focus at the long distance side, by generation of one pulse of a focusing motor driving the focus driving mechanism intended for putting the lens system in focus, the lens system is out of focus again, this time at the short distance side.
Generally, a focus adjusting mechanism is designed such that a lens system or a CCD as a photographing element is moved about one half of a depth of focus by one pulse of a focusing motor driving the focus adjusting mechanism. Of course, the lens system or CCD may be moved at a finer resolution from the viewpoint of performance, which, however, is disadvantageous from the viewpoint of driving time. Therefore, in this disclosure, it is assumed that a lens system or a CCD as a photographing element is moved one half of a depth of focus by one pulse of a focusing motor driving a focus adjusting mechanism for moving the lens system or the CCD.
The number of driving pulses of the focusing motor for moving the lens system or CCD for focus adjustment are calculated as illustrated in FIG. 10 and FIG. 11. The F-number and the focal distance of the lens system and the picture element pitch of the CCD are predetermined, respectively. For adjusting the focus in the range of photographing distance between infinity distance and the distance of 30 cm, for example, in a telephotographing condition, the focusing motor is driven for about 100 pulses. That is, by driving the focusing motor for this number of pulses, i.e., about 100 pulses, the lens system or CCD is moved through the whole scanning width for adjusting the focus. High frequency components of image signals obtained from the CCD in the whole scanning width are sampled and evaluated at appropriate intervals, and based upon a result of the evaluation, the focused position is determined. It is not necessary to obtain an evaluation value for each pulse of the focusing motor, and for example, an evaluation value may be obtained for every 3-4 pulses and thereafter an interpolating calculation may be performed. The length of an auto-focusing time is greatly affected by width of the whole scanning width for focus adjustment.
The whole scanning width for focus adjustment is greater as the CCD picture element pitch is finer, the F-number is brighter, the focal length is longer, or the closest photographing distance is smaller. Accordingly, in recent digital cameras, the auto-focusing time tends to be increased.
To cope with such a problem that the auto-focusing time is increased, a short distance photographing mode (hereinafter, a macro photographing mode) is often provided.
For example, in a camera having a lens system designed for photographing an object in the range of distance between infinity distance and the closest distance of 30 cm, when a normal photographing mode is selected, the photographing range is set to be between infinity distance and the distance of 60 cm, and when a macro photographing mode is selected, the photographing range is set to be between the distances of 60 cm and 30 cm. Thereby, in either of the normal photographing mode and the macro photographing mode, the whole scanning width of a range of distance in which the lens system or a CCD as a photographing element is moved for focus adjustment is reduced such that by driving a focusing motor for about 50 pulses, the lens system or CCD is moved through the whole scanning width for focus adjustment, so that the auto-focusing time is remarkably reduced.
In background cameras, selection of a normal photographing mode and a macro photographing mode is performed by manipulating a dial-type mode selection switch, which is separate from a release button with which an instruction of auto-focusing is given by a halfway depressing operation thereof. The photographer first manipulates the mode selection switch to select, for example, the normal photographing mode, and then depresses the release button halfway, and thereby auto-focusing in the normal photographing mode is performed. When the release button is halfway depressed after selecting the macro photographing mode, auto-focusing in the macro photographing mode is performed.
As described above, in the background cameras having a macro photographing mode, when photographing an object at a closest distance, before manipulating a release button, a mode selection switch must be manipulated to select the macro photographing mode, which is troublesome. In particular, when photographing moving objects, such as children, at a shorter distance, and another objects at a normal distance, at random, switching between the normal and macro photographing modes is extremely troublesome.
Further, some recent digital cameras are provided with two macro photographing modes, such as a normal macro photographing mode for photographing an object in the range of distance from 30 cm to 60 cm and a super macro photographing mode for photographing an object in the range of distance from 1 cm to 30 cm. In such digital cameras, the operation of selecting one of the photographing modes is more time consuming, leading to a problem that a photographing chance is missed.
Furthermore, in some recent cameras, in addition to the normal photographing mode and the macro photographing mode, various other photographing modes are provided, for example, a single auto-focusing mode in which an auto-focusing operation is performed only once in response to a halfway depressing operation of a release button, and a continuous auto-focusing mode in which an auto-focusing operation is performed while the release button is continued to be halfway depressed.